These are not simply differences of opinion. These are denials and attacks. Why do these attitudes keep arising? There isn’t a single reason:

The speaker may genuinely believe the various statements. This must surely be based on ignorance and a very narrow world view. There is too much evidence in the world that atheists can’t all, or even mostly, be like that!

The speaker may be lying for the sake of the audience. (“Lying for Jesus” is a common trait). Perhaps the speaker believes it is to the advantage of the audience not to accept atheist as a viable world-view, or perhaps the speaker believes it is to the speaker’s own advantage!

The speaker may be afraid for it even to be known that atheists exist. For example, Monique Davis, member of the Illinois House of Representatives, famously said: “I don’t know what you have against God, but some of us don’t have much against him…. This is the land of Lincoln where people believe in God… What you have to spew and spread is extremely dangerous… It’s dangerous for our children to even know that your philosophy exists…”

The speaker may perceive what others are saying through a filter. For example, many religious people perceive Richard Dawkins as being “shrill”. Here is a polite “English gentleman” who speaks calmly in measured tones! But he says things that many people don’t want to hear.

And there are probably several other reasons too, and variations and combinations of these.

These statements are analogous to attempts to convert atheists, even where that is not the primary purpose. Here is my attempt to help religious people prepare for this before wasting their time: